We use a simple framework where firms in two countries serve their respective domestic markets and a world market to analyse under which conditions cost-reducing mergers will be beneficial for the merging firms, the home country, and the world as a whole. For a national merger, the policies enacted by a national merger authority tend to be overly restrictive from a global efficiency perspective. In contrast, all international mergers that benefit the merging firms will be cleared by either a national or a regional regulator, and this laissez-faire approach is also globally efficient. Finally, we allow for multiple mergers and analyse whether national mergers, international mergers or no mergers will be the equilibrium market structure when ...